Numerous industries and many applications utilize metallic tubes, fittings, and various other “plumbing” components for handling and controlling critical fluid flow. Such components may be made of copper, stainless steel, and steel. Where the fluids being handled are under significant pressure or where containment integrity is critical, seals such as O-rings and flexible flat gaskets are typically utilized.
In particular applications such as semiconductor processing, the fluids involved react with and/or may be contaminated by the use of metallic components and conventional gaskets and elastomeric O-rings. Thus, in such industries, plumbing components are made of highly inert materials such as fluoropolymers, i.e., PFA and PTFE, for wetted components. In such applications, elastomeric O-rings are typically formed of two materials with a first traditional elastomeric material, such as silicon, encapsulated in a fluoropolymer coating. These O-rings are expensive and are subject to degradation and are typically considered to be single use.
Various fluoropolymer-based fittings and couplings have evolved for making connections between fluoropolymer components that do not utilize O-rings. Referring to Prior Art FIG. 1, one typical type of fitting is known in the industry as a FLARETEK® fitting. FLARETEK is a registered trademark of Fluoroware, Inc., the assignee of this patent application. In such a fitting 30 the elongate tapered nose section 32 with a threaded neck 34 engages within a tubular end portion 36 which is flared to fit over the tapered nose section. The flared section 38 will have an inside cylindrical surface 40 that has an inside diameter sized for the outside diameter of an outside cylindrical surface 42 of the nose section 32. The nose section thus “telescopes” into the flared section 38. A nut 44 tightens the flared section onto the nose creating a seal 46 between the fitting body and the flared portion of the tubing portion. The flared end of the tubing is generally formed by heating the tubing and shaping the heated malleable tubing end into the desired flared configuration using steel forms.
Various other types of fluoropolymer fittings are known in the art. Some utilize separate gripper portions or internal ferrules. See for example U.S. Pat. Nos. 3,977,708 and 4,848,802. For connections between fluoropolymer valves and components such as fluoropolymer manifolds, sealing integrity between the components is typically accomplished by gaskets or fluoropolymer covered O-rings. In certain instances annular tongue-in-groove connections without O-rings or gaskets have been successfully utilized. These connections have the disadvantage that they must be precisely machined, i.e., tolerances of 0.0005 inches, and it can be difficult to properly align the mating pieces. Moreover, such connections are vulnerable to nicks and scratches which can compromise the integrity of the connection. Such a tongue-in-groove fitting is illustrated by U.S. Pat. No. 5,645,301. U.S. Pat. Nos. 3,977,708, 4,848,802, and 5,645,301 are incorporated herein by reference.